1. Field of the Invention
The present invention relates to micro-electromechanical systems (MEMS) gyros, and more particularly to systems and methods that isolate vibration induced movements therein.
2. Description of Related Art
Micro-electromechanical systems (MEMS) integrate electrical and mechanical components on the same substrate using micro-fabrication technologies. The electrical components are fabricated using integrated circuit processes, while the mechanical components are fabricated using micromachining processes that are compatible with the integrated circuit processes. This combination makes it possible to fabricate an entire system on a chip using standard manufacturing processes. MEMS devices are commonly applied in design and manufacture of sensor devices, where the mechanical portion of the sensor device provides the sensing capability, and the electrical portion of the sensor device processes the information received from the mechanical portion.
One example of a MEMS device is a gyroscope or gyro, which can measure rotation. Specifically, MEMS gyros rely on conservation of momentum of a structure having limited oscillation motion, e.g., vibrating elements, to detect a Coriolis force and determine angular rate of rotation about an input axis. However, these vibrating elements are inherently resonant and are susceptible to additional oscillatory movements occurring outside desired axes of rotation. That is, the vibrating elements within a MEMS gyro can dynamically gain additional oscillatory movements when they resonate and incur common mode oscillations, which can cause undesired and erroneous outputs. For example, MEMS gyros are oriented and mounted to a body, e.g., an aircraft, via a suspension system. When the suspension system converts a vibration into a rotational oscillation about an input axis, a false rotation signal is generated—this is an “out of balance” condition. A loose suspension lets a gyro mass move independently from the frame thereby allowing false rotations. Further still, as the suspension system degrades with time, temperature, or other aging effects, the suspension system can stiffen and no longer isolate the MEMS die causing false rotation signals. Put simply, any vibration at a frequency that excites the output mode resonance creates errors in the output signal. Moreover, although conventional suspension systems have generally been considered satisfactory for applications where vibration isolation is needed in all directions, improved vibration isolation for MEMS devices is desired.
Despite design efforts to date, eliminating additional and undesired vibrations in conventional MEMS devices remains problematic. Accordingly, there is still a need in the art for systems and methods of isolating and attenuating vibration in an axis specific fashion. The present invention provides a solution for these problems.